Prox1 Suppresses Proliferation and Drug Resistance of Retinoblastoma Cells via Targeting Notch1.

Objective: Retinoblastoma (RB) is a prevalent type of eye cancer in youngsters. Prospero homeobox 1 (Prox1) is a homeobox transcriptional repressor and downstream target of the proneural gene that is relevant in lymphatic, hepatocyte, pancreatic, heart, lens, retinal, and cancer cells. The goal of this study was to investigate the role of Prox1 in RB cell proliferation and drug resistance, as well as to explore the underlying Notch1 mechanism.
Methods: Human RB cell lines (SO-RB50 and Y79) and a primary human retinal microvascular endothelial cell line (ACBRI-181) were used in this study. The expression of Prox1 and Notch1 mRNA and protein in RB cells was detected using quantitative real time-polymerase chain reaction (RT-qPCR) and Western blotting. Cell proliferation was assessed after Prox1 overexpression using the Cell Counting Kit-8 and the MTS assay. Drug-resistant cell lines (SO-RB50/vincristine) were generated and treated with Prox1 to investigate the role of Prox1 in drug resistance. We employed pcDNA-Notch1 to overexpress Notch1 to confirm the role of Notch1 in the protective function of Prox1. Finally, a xenograft model was constructed to assess the effect of Prox1 on RB in vivo.
Results: Prox1 was significantly downregulated in RB cells. Overexpression of Prox1 effectively decreased RB cell growth while increasing the sensitivity of drug-resistant cells to vincristine. Notch1 was involved in Prox1's regulatory effects. Notch1 was identified as a target gene of Prox1, which was found to be upregulated in RB cells and repressed by increased Prox1 expression. When pcDNA-Notch1 was transfected, the effect of Prox1 overexpression on RB was removed. Furthermore, by downregulating Notch1, Prox1 overexpression slowed tumor development and increased vincristine sensitivity in vivo.
Conclusion: These data show that Prox1 decreased RB cell proliferation and drug resistance by targeting Notch1, implying that Prox1 could be a potential therapeutic target for RB.
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